Determines how much axial load a screw must withstand without breaking. If full size screws are tested, the yield strength can only be approximately established. Under ISO 898 Part 1, the exact yield strength and elongation after fracture can be determined using machined specimens. Exceptions are stainless steel screws A1 to A4 (ISO 3506).

Tensile strength Rm


Tensile strength at rupture in thread:

Rmmax. tensile force F/stress area        [N/mm2]


Tensile strength at rupture in cylindrical shank:

Rmmax. tensile force F/ initial cross section of specimen        [N/mm2]


 [N/mm2] = 1 MPa = 145.03 psi



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